Indicators for the direction of travel, referred to as direction indicators, are required for applications in vehicles. A direction indicator has the function of using a lighting means to indicate to other road users if the road user wishes to change the direction of travel. Direction indicators have been implemented electromechanically, efforts being made to replace these electromechanical solutions by more economical electronic ones. A contemporary direction indicator is composed of a direction indicator circuit, a direction indicator switch and a plurality of lighting means, for example incandescent lamps. Since an electronic solution is intended to replace an established electromechanical solution, value is placed on a direction indicator circuit which is as economical as possible and on an overall solution which is an economical as possible. The direction indicator circuit, the direction indicator switch and the lighting means are connected in series between the supply voltage and the vehicle ground or a ground terminal of the vehicle. If the direction indicator switch is closed, the lighting means is to flash with a defined frequency, that is to say light up or not light up periodically. The frequency is defined as 1.5 Hz or 3 Hz, wherein the frequency of 3 Hz indicates a fault in a lighting means.
Direction indicator circuits in vehicles are used in environments which are very demanding in terms of the robustness and the reliability of the direction indicator circuit and the direction indicator per se. Direction indicators are subject to low and high temperatures, a high degree of humidity, to soiling and dirt of all types. Owing to these stresses, a conductive path can be formed between the direction indicator circuit and the vehicle ground. If such a path is present, the capacitor can be charged even though the direction indicator circuit is not closed. If the capacitor is sufficiently charged, the direction indicator circuit also operates. That is to say that the direction indicator circuit opens its internal switch and closes. This does necessarily have to bring about unintended lighting up of the direction indicator since the direction indicator switch is open. The problem arises that the direction indicator circuit is not started from a defined operating state. This may result in a situation in which the first time period in which the lighting means of the direction indicator lights up the first time is too short. In the worst conceivable case it may be that the direction indicator switch is closed while the switch of the direction indicator circuit has just been switched off. In this case, the capacitor will not charge as quickly as possible, as in the case of normal powering up, but instead with a charge current which is typical of the off state, with the result that the time until the lighting means of the direction indicator first lights up is greatly lengthened.
Such a moment at which the lighting means of the direction indicator lights too briefly is undesired and is to be avoided.